Decoding apparatus, decoding method, and non-transitory computer readable medium

Abstract

A decoding apparatus includes a multi-input branch metric calculation unit configured to calculate, by using a branch label corresponding to a path extending toward a state S at a time point N in a trellis diagram and a plurality of reception signal sequences, a branch metric in the state S, a path metric calculation unit configured to calculate a path metric in the state S at the time point N, and a surviving path list memory configured to store path labels corresponding to L path metrics among a plurality of calculated path metrics. The path metric calculation unit generates a path label in the state S at the time point N by combining the branch label with a path label in each of the states at the time point N−1 and the surviving path list memory outputs path labels corresponding to L path metrics.

The invention claimed is: 
     
       1. A decoding apparatus comprising:
 at least one memory storing instructions, and 
 at least one processor configured to execute the instructions to;
 calculate, by using a branch label corresponding to a path extending toward a state S (S is an integer no less than zero) at a time point N (N is an integer no less than zero) in a trellis diagram and a plurality of reception signal sequences, a branch metric in the state S; 
 calculate a path metric in the state S at the time point N by adding the branch metric in the state S at the time point N to a path metric in each of states at a time point N−1, each of which forms a path with the state S at the time point N; and 
 store path labels corresponding to L path metrics (L is an integer no less than one) among a plurality of calculated path metrics, 
 generate a path label in the state S at the time point N by combining the branch label with a path label in each of the states at the time point N−1, each of which forms a path with the state S at the time point N, and 
 output, as a transmission signal sequence, path labels corresponding to L path metrics selected at an end point in the trellis diagram; and 
 
 one or more hardware calculation units each including L successive cancelation (SC) units, each of the SC units is configured to perform decoding processing of a Polar code having a length of N 1  bits (N 1  is an integer no less than one), each of the SC units having a list size of 1, 
 wherein the at least one processor is further configured to execute the instructions to calculate the branch metric by using L reception signal sequences each having a length of N 2  bits and the branch label, the L reception signal sequences being ones output from N 2  hardware calculation units (N 2  is an integer no less than one). 
 
     
     
       2. The decoding apparatus according to  claim 1 , wherein the at least one processor is further configured to execute the instructions to store an index specifying the reception signal sequence that is used to calculate the path metric. 
     
     
       3. The decoding apparatus according to  claim 2 , wherein the at least one processor is further configured to execute the instructions to store the calculated path metric, and
 add the branch metric calculated by using the reception signal sequence indicated by the index to a path metric in each of states at the time point N−1 stored in the path metric memory. 
 
     
     
       4. The decoding apparatus according to  claim 1 , wherein the at least one processor is further configured to execute the instructions to store path labels corresponding to L path metrics in ascending order of their values among the plurality of calculated path metrics. 
     
     
       5. The decoding apparatus according to  claim 1 , wherein
 for an end point in the trellis diagram, the number of states is one, and 
 the at least one processor is further configured to execute the instructions to calculate a path metric corresponding to a path extending toward one state at the end point in the trellis diagram, and generates a path label. 
 
     
     
       6. A decoding method comprising:
 calculating, by using a branch label corresponding to a path extending toward a state S (S is an integer no less than zero) at a time point N (N is an integer no less than zero) in a trellis diagram and a plurality of reception signal sequences, a branch metric in the state S; 
 calculating a path metric in the state S at the time point N by adding the branch metric in the state S at the time point N to a path metric in each of states at a time point N−1, each of which forms a path with the state S at the time point N; 
 storing path labels corresponding to L path metrics (L is an integer no less than one) among a plurality of calculated path metrics; 
 generating a path label in the state S at the time point N by combining the branch label with a path label in each of the states at the time point N−1, each of which forms a path with the state S at the time point N; and 
 outputting, as a transmission signal sequence, path labels corresponding to L path metrics selected at an end point in the trellis diagram, wherein 
 the method further comprises: 
 performing, using one or more hardware calculation unit each including L successive cancelation (SC) units, decoding processing of a Polar code having a length of N 1  bits (N 1  is an integer no less than one), each of the SC units having a list size of 1, and 
 calculating the branch metric by using L reception signal sequences each having a length of N 2  bits and the branch label, the L reception signal sequences being ones output from N 2  hardware calculation units (N 2  is an integer no less than one). 
 
     
     
       7. A non-transitory computer readable medium storing a program for causing a computer to:
 calculate, by using a branch label corresponding to a path extending toward a state S (S is an integer no less than zero) at a time point N (N is an integer no less than zero) in a trellis diagram and a plurality of reception signal sequences, a branch metric in the state S; 
 calculate a path metric in the state S at the time point N by adding the branch metric in the state S at the time point N to a path metric in each of states at a time point N−1, each of which forms a path with the state S at the time point N; 
 store path labels corresponding to L path metrics (L is an integer no less than one) among a plurality of calculated path metrics; 
 generate a path label in the state S at the time point N by combining the branch label with a path label in each of the states at the time point N−1, each of which forms a path with the state S at the time point N; and 
 output, as a transmission signal sequence, path labels corresponding to L path metrics selected at an end point in the trellis diagram, wherein 
 the non-transitory computer readable medium is configure to further cause the computer to: 
 perform, using one or more hardware calculation unit each including L successive cancelation (SC) units, decoding processing of a Polar code having a length of N 1  bits (N 1  is an integer no less than one), each of the SC units having a list size of 1, and 
 calculate the branch metric by using L reception signal sequences each having a length of N 2  bits and the branch label, the L reception signal sequences being ones output from N 2  hardware calculation units (N 2  is an integer no less than one).